This invention is directed toward the field of facsimile machines and more particularly is directed toward the field of facsimile machines which employ a cathode ray tube to record an image on a photo sensitive medium.
Systems which record image data into a permanent form are well known in the art. To form a permanent record of an image, the image data is presented on a cathode ray tube (CRT) in close proximity to a reproduction medium such as photographic film or dry silver reproducing paper. The full image is then projected onto the reproduction medium essentially at once. The reproduction medium may be further processed by heating or treatment with chemicals. However, because the full image is projected as a unit onto the reproduction medium, this method of recording requires large amounts of memory due to the amount of data that needs to be stored and transferred at any given time.
Thus, systems which produced only one line of a larger video image were developed. U.S. Pat. No. 4,309,720 (Denham) shows such a system. A full image is broken up into a plurality of lines, each line further being broken into separate color components. Then, the separate color components of a plurality of different lines are sequentially presented at a CRT. The CRT has a red phosphor, a green phosphor, and a blue phosphor, which are capable of displaying only a portion of the larger video image. After one color component each of a plurality of lines has been sequentially displayed on the CRT face, the reproduction medium is moved so that a new plurality of color components of a plurality of lines can be presented to the CRT face and these new components will be exposed on an area of the reproduction medium not previously exposed to those components. Yet, it is desirable to have a system where the size and resolution of the recorded image are variable.